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Visible-light-driven photo-fenton-like catalytic activity and photoelectrochemical (PEC) performance of nitrogen-doped brownmillerite KBiFe2O5 (KBFO) are investigated. The effective optical bandgap of KBFO reduces from 1.67 to 1.60 eV post N-doping, enabling both enhancement of visible light absorption and photoactivity. The photo-fenton activity of KBFO and N-doped KBFO samples were analysed by degrading effluents like Methylene Blue (MB), Bisphenol-A (BPA) and antibiotics such as Norfloxacin (NOX) and Doxycycline (DOX). 20 mmol of Nitrogen-doped KBFO (20N-KBFO) exhibits enhanced catalytic activity while degrading MB. 20N-KBFO sample is further tested for degradation of Bisphenol-A and antibiotics in the presence of H2O2 and chelating agent L-cysteine. Under optimum conditions, MB, BPA, and NOX, and DOX are degraded by 99.5% (0.042 min-1), 83% (0.016 min-1), 72% (0.011 min-1) and 95% (0.026 min-1) of its initial concentration respectively. Photocurrent density of 20N-KBFO improves to 8.83 mA/cm2 from 4.31 mA/cm2 for pure KBFO. Photocatalytic and photoelectrochemical (PEC) properties of N-doped KBFO make it a promising candidate for energy and environmental applications. [ABSTRACT FROM AUTHOR]

To the best of our knowledge, we report for the first time the growth of brownmillerite Ca2Fe2O5 (CFO) single crystals under Argon (Ar) only ambience by optical floating zone (OFZ) technique and compare its structural and spectroscopic properties with CFO single crystals grown by OFZ method under air and oxygen (O2) atmospheres. Single-crystal X-ray diffraction confirms growth of Ca2Fe2O5 single crystals in all the atmospheres. Crystals grown in air and oxygen (O2) atmospheres show both metallic Fe0 and Fe3+states, whereas in Ar-grown crystals only Fe3+ oxidation state is observed. An enhancement in oxygen vacancies is also observed in Ar-grown crystals. Growth ambience is found to have a strong influence on cationic environment and binding energy of constituent elements, as is evident from the X-ray photoelectron spectroscopy of the Ca2Fe2O5 crystals. [ABSTRACT FROM AUTHOR]

A simple and easy method of synthesis and catalyst-free deposition of few layer graphene (FLG) on non-conducting sapphire substrates still remains a challenge. This work involves preparation of FLG by liquid exfoliation method and deposition of FLG onto chemically etched sapphire substrate with and without catalyst by drop casting technique. Field emission scanning electron microscopy (FESEM) was used to observe presence of FLG on sample surfaces and its energy dispersive X-ray (EDX) spectra reveals absence of other trace impurity. Atomic force microscopy (AFM) shows FLG within and along the sidewalls of the dislocation site for catalyst free sample. Fourier transform infrared spectroscopy confirmed the dispersion of FLG in solvent. Raman spectroscopy revealed prominent graphene peak positions corresponding to D, G and 2D bands. Also, diamond like carbon, fullerene and additional Raman modes have been observed using Raman spectroscopy excited at higher wavelength. FESEM, EDX and AFM results prove better FLG dispersions on catalyst-free sample in comparison to sample with catalyst. This method of FLG deposition will be highly suitable for optoelectronic applications for developing cost-efficient device with optimum performance. [ABSTRACT FROM AUTHOR]

In this article, we report ourrecentresults on the synthesis of nano-ink and drop-casted films of CuInGaS2(CIGS), which acts as the absorber material for CIGS-based solar cells. The morphological and optical property changes of CIGS films have been compared to those of nano-CuInS2(CIS) films deposited on glass substrates. It is found that the microstructure and morphology of these films depend strongly on the presence of Ga. High-resolution transmission electron microscopy reveals that CIGS nanoparticles are 4–5 times larger than CIS nanoparticles. The roughness of CIGS films could be reduced on preheating the drop-casted films prior to sulphurisation. The absorption onset for CIGS is lower than that of CIS due to Ga substitution in place of In. Raman spectra showed a noticeable contribution from Cu–Au mode in CIGS films. Larger nanoparticles in CIGS are attributed to faster growth kinetics due to higher Cu:In ratio than in CIS. [ABSTRACT FROM PUBLISHER]

Visible-light-driven photo-fenton-like catalytic activity and photoelectrochemical (PEC) performance of nitrogen-doped brownmillerite KBiFe2O5 (KBFO) are investigated. The effective optical bandgap of KBFO reduces from 1.67 to 1.60 eV post N-doping, enabling both enhancement of visible light absorption and photoactivity. The photo-fenton activity of KBFO and N-doped KBFO samples were analysed by degrading effluents like Methylene Blue (MB), Bisphenol-A (BPA) and antibiotics such as Norfloxacin (NOX) and Doxycycline (DOX). 20 mmol of Nitrogen-doped KBFO (20N-KBFO) exhibits enhanced catalytic activity while degrading MB. 20N-KBFO sample is further tested for degradation of Bisphenol-A and antibiotics in the presence of H2O2 and chelating agent L-cysteine. Under optimum conditions, MB, BPA, and NOX, and DOX are degraded by 99.5% (0.042 min-1), 83% (0.016 min-1), 72% (0.011 min-1) and 95% (0.026 min-1) of its initial concentration respectively. Photocurrent density of 20N-KBFO improves to 8.83 mA/cm2 from 4.31 mA/cm2 for pure KBFO. Photocatalytic and photoelectrochemical (PEC) properties of N-doped KBFO make it a promising candidate for energy and environmental applications. [ABSTRACT FROM AUTHOR]

Heterojunction photocatalysts have recently emerged for use in degradation of organic pollutants, typically being suspended in effluent solution to degrade it. Post degradation, the catalyst must be removed from the treated solution, which consumes both energy and time. Moreover, the separation of nano catalysts from the treated solution is challenging. In the present work, we explore fabrication of immobilized TiO 2 -PEDOT:PSS hybrid heterojunction catalysts with the support of a PVA (polyvinyl alcohol) matrix. These photocatalytic films do not require any steps to separate the powdered catalyst from the treated water. While the PVA-based films are unstable in water, their stability could be significantly enhanced by heat treatment, enabling efficient removal of organic effluents like methylene blue (MB) and bisphenol-A (BPA) from the aqueous solution under simulated sunlight irradiation. Over 20 cycles, the heterojunction photocatalyst maintained high photocatalytic activity and showed excellent stability. Hence, an immobilization of the TiO 2 -PEDOT:PSS hybrid heterojunction is suggested to be beneficial from the viewpoint of reproducible and recyclable materials for simple and efficient wastewater treatment., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

KBiFe 2 O 5 (KBFO) is an upcoming promising brownmillerite-structured multiferroic photoactive material for next-generation photovoltaic and photocatalytic applications. In the present work, KBFO has been developed using multistep thermal treatment method to reduce the volatility of constituent elements and improve the stability of compound. The band gap of KBFO (found to be ∼1.68 eV) extends to the near-infrared region compared to traditional perovskite-structured multiferroics. The magnetic and dielectric transitions occur in the same temperature range (740 K-800 K), reflecting the existence of magneto-dielectric effect in the as-synthesized sample. It also shows promising photocatalytic activity by degrading organic effluents under natural sunlight compared to regular perovskite BiFeO 3 photocatalyst (operating under visible light). A new application of brownmillerite multiferroic KBFO photocatalyst in environmental and energy applications has been explored by integrating the structural, optical, magnetic, and dielectric properties of the same., Competing Interests: The authors declare no competing financial interest.